Shaded pole motor construction



Aug. 5, 1952 K. BURIAN SHADED POLE MOTOR CONSTRUCTION Original FiledOct. 17, 1947 ZSHEETS-SHEET 1 INVEN TOR KURT BUR/ Aug. 5, 1952 BURlAN2,606,223

SHADED POLE MOTOR CONSTRUCTION Original Filed Oct. 17, 1947 2Sl-lEETS-SPEET 2 IN 1 'EN TOR KURT BURIAN (A) Mi 1- W 7 Patented Aug. 5,1952 SHADED POLE MOTOR CONSTRUCTION Kurt Burian, Chicago, 111., assignorto G-M Laboratories, Inc., Chicago, 111., a corporation of IllinoisOriginal application October 17, 1947, Serial No.

780,410. Divided and this application November 15, 1950, Serial N0.195,859

lClaim.

Thi invention relates to an improved construction of relatively smallmotors such as the type disclosed in Stewart et a1. Patent No.1,822,679. This application is a division of application Serial No.780,410, filed October 17, 1947 by William H. Kitto and Kurt Burian.

Motors of the type identified have a tendency to produce excessivenoise, particularly when employed under conditions where there may be avariable thrust load. By careful study of such motors, it has beendetermined that the noise is in part caused by and in part aggravated byseveral factors, some of which, in the first instance, appear to beunrelated. Among the causes of the noise were vibrations produced byaxial thrust, as when intermittent contact occurs between the rotatingsystem and stationary parts, such as bearings, vibrations due to unequalresistances in th shading coil loops on opposite sides of the rotor andmechanical vibration of such loops due to alternation of the magneticfield in the stator, the latter being aggravatedsomewhat, possibly, bythe first described axial thrust factor. So far as axial thrust isconcerned, this becomes directly related to the bearing system, and thebearing system again involves lubrication, both of which have been takeninto consideration in the improved construction which is employed. Suchportion of the noise as is due to the shaded pole loops, is eliminatedby providing a single piece stamping which is common to both loops of apair and which links the loops together to complete the circuit betweentwo U-shaped loop parts.

The principal object of the invention is the provision of an improved,relatively small, electric motor.

Another object is the provision of an electric motor which secures theadvantages and overcomes the problems discussed hereinabove.

A motor constructed in accordance with the present invention is shown inthe accompanying drawings wherein:

Fig. 1 is a perspective view;

Fig. 2 is an exploded view showing the rotor and bearing assembliesseparated from each other;

Fig. 3 is a transverse sectional view taken on the line 33 of 'Fig. 1;

Fig. 4 is a fragmentary perspective view of the stator;

Fig. 5 is a fragmentary plan view of the stator with two of the shadingloops broken away to illustrate structure;

Fig. 6 is a sectional view taken on the line 6-6 of Fig. 5;

Fig. 7 is an enlarged exploded view of the shading loop assembly;

Figs. 8 and 9 are enlarged perspective views of a flat and resilientsteel washer, respectively;

Fig. 10 is an enlarged sectional view taken on the line 10-40 of Fig. 3;and

Fig. 11 is a transverse plan sectional view taken on the line Il-ll ofFig. 10.

Referring now to the drawings, the motor of the invention comprises astator with the usual stack I2 of ferro-magnetic laminations, suitablyshaped to provide stationary poles and having at least one alternatingcurrent coil 13. It also comprises a suitable rotor 14 secured to arotor shaft l6 adapted to be journalled in bearing assemblies 1'1. Thelaminations are stamped to provide an opening 18 in which the rotor isadapted to rotate, opposite sides of the opening 18 forming the usualpole areas of a motor of this type.

The poles have unshaded, shaded and double.

shaded portions with slots l9 between such portions. Shading isaccomplished by means of the usual copper loops. In accordance with thisinvention the copper loops comprise two U -shaped loop members 21 and 22and a common connecting member 23 having recesses for receiving the endsof the two U-shaped loop members. The U-shaped' and connecting membersare formed of copper or other suitable highly conductive material andare secured together to form a substantially single piece assembly bysoldering or brazing. I

The bearing assemblies comprise a bearing bracket 24 to which is rivetedan open cupshaped member 26 within which is disposed a sintered, porousbearing 21 in which the shaft I6 is journalled (see Fig. 10) and an oilreservoir 28. A retainer 29 in the form of a spider completes theassembly. 1

Between the bearing 21 and rotor 14 is provided a split resilient washer31, whose normal shape is shown in Fig. 9, and a flat washer 32 withprojections 33, in the nature of embossments, which fall in the slitsformed by the split and extending portions 34 of the resilient washer3|. The relationship of the two washers is shown particularly in Figs.10 and 11.

The motor is assembled by producing a subassembly of the laminations l2and coil [3 in a usual manner and then assembling the shading loopstherewith. The rotor is then placed in position and the bearingassemblies secured in position by means of bolts 36 and suitable nuts31. After assembly, an oil slinger 38 is forced into position on theshalt [6 so as to lie Within a cup-shaped boss 39 formed on the bearingbracket IT. The slinger need be applied only to one side of the shaft l6when one short end is provided, as shown in the drawings, because theend of the shaft lying within the'cup-shaped portion 39 can, itself, actas a slinger.

The construction described has advantages other than in the eliminationof noise, although i the latter is very important in the design as awhole. It will be noted thatth'e resilient washer lies with its planesurface: against the.

end of the rotor and the flatwasherhas its plane surface against the endof the sintered bearing. When these two washers are brought intocontact, the embossment s oifitlieflat washer it is'possible :to solveboth the problem of variable 'thrustandjsuppression of oil leakage.

The elimination of noise is further enhanced by the use of. a connectioncommon to both shading 1pcsp Thebonstruction described not automaticallyposition themselves between the f split portions of the resilient washerandcause the two washers to turn together. sufficient friction betweenthe relatively larger resilient washer and the rotorto cause the two torotate together With negligible slippage and this tendency is furtherassured by the magnetic attraction which the rotor hasfor the resilientwasher. The fiat washer is then-caused to rotate with the rotor assemblyand the relative movement is, therefore, between the oily face of thebearing and the-fiat washer. Thus, friction and Wear are greatly reducedby reason of 'maintaining an oil film between these two moving surfaces.

It is found that there is considerable tendency for oil to be dischargedfromsintered porous bearings and if the oil is suitably confined, adefinite circulation canbe traced. It is, therefore, important to avoidmovement of the oil along the shaft and at one side this may be takencare ofby the slinger arrangement described. At theinside face of thebearing, the flat washer tends to return the oil to the bearingreservoir and this tendency is maintained by the relative'diameters ofthe twowashers. It is found that if the flat washer is larger than theportions 34 of the resilient'washer, then oil will not be transferredfrom'the flat washer to the resilientwasher and thence to the rotor, butwill be retainedby the bearing while if the flat washer is smaller, thentransfer does take place. It will be noted that-the flat washer hasabout the same diameter as the adjacent portion of the bearing, andafilm'or meniscus of oil will be "maintained between-these parts.

One of the principal advantages of the structure describedis theelimination of noise caused by intermittent contact of; the rotatingsystem and stationary bearings-when there is a variable thrust load.- Inthe past, washers of felt, oilproof rubber and the like have beenemployed for the'purpose of absorbing energy of impact of the movingsystem against the bearing face. While noise has been prevented by thismeans, it has been impossible to retain the oil. suitably;

There is .onlyreduces cost; but makes it possible to maintain moreuniform and lower loop resistances than by other methods heretoforeemployed. The relatively wide area of contact of the connecting linkwith'the stator, and the connecting of thetw'o' loopstogether'mechanically reduces vibration. The better soldering whichresults from the use of this construction causes the electricalresistance tobe more uniform and thereby also reduces vibration.

What I claim as new and desire to protect by Letters Patent of theUnited States is:

-In a motor' of the character describedincluding a stator having atleasttwo poles,each in turn provided with a pair of slots extendingtherethrough from side to side, a coil operably associated with thepoles and a rotor journalled to rotate between the poles, a shading'loopconstruction for each polebomprisingg a first U- shaped loop memberhaving one 'of its' legs receivedin-o'ne of the slotsfa second U-shapedloop member having one of its legs received in the othe'r slot,'thbthrle'gs of the U-shaped loop members lying adjacent each other andtheiencl s oif t he legs of the U-shaped loop members all terminatingadjacent'one side of the pole} and-a "relativelywide"common bridgememberj en thats'ide of the pole and having recesses for receiving theends opth'e legs of both U- Shapedloopjnembers said commonbridge memberbeing secur'd 'tothe ends of'the legs of both U 'shaped-loopfmembers,

U TB R RE saaNoEs crrEn ev f llowin new e ao re ard in. the

filetflith sna 1. i

' 'I IT D srAT s aT rs Number I Name Date 1',036,75 'z- Walker Aug. 27,1912 1,822,679 Stewart et a1. sept. 8,1931 2.2511373 qillen Aug. 5,19412,467,755 Koch Apr. 19, 1949 Morris l Nov. 8.11949

